DB basics SQL

Question

The maximum length of an attribute of type text is

• A. 127
• B. 255
• C. 256
• D. It is variable

Comments

256

Answer 1

Answer would be (D) It is variable.

TINYBLOB, TINYTEXT                       L + 1 bytes, where L < 2^8
BLOB, TEXT                                      L + 2 bytes, where L < 2^16
MEDIUMBLOB, MEDIUMTEXT            L + 3 bytes, where L < 2^24
LONGBLOB, LONGTEXT                     L + 4 bytes, where L < 2^32

Variable-length string types are stored using a length prefix plus data. The length prefix requires from one to four bytes depending on the data type, and the value of the prefix is L (the byte length of the string). For example, storage for a MEDIUMTEXT value requires L bytes to store the value plus three bytes to store the length of the value.

Here is the Reference. 

Comments

Is it char or var char ?

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check the reference.

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may be its 256.I'm not sure.  (0<M<255)

#ref : 

In the following table, M represents the declared column length in characters for nonbinary string types and bytes for binary string types. Lrepresents the actual length in bytes of a given string value.

Data Type	Storage Required
CHAR(M)	M × w bytes, 0 <= M <= 255, where w is the number of bytes required for the maximum-length character in the character set. See Section 15.2.6.7, “Physical Row Structure” for information about CHAR data type storage requirements for InnoDB tables.

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Given here .  the size of a text column is 256 if size <= 256 (where size represents the size of the row); otherwise, the size is 256 + size + (2000 − (size − 256) % 2000).

And also a VARCHAR(255) column can hold a string with a maximum length of 255 characters. Assuming that the column uses the latin1 character set (one byte per character), the actual storage required is the length of the string (L), plus one byte to record the length of the string.

So how can you ensure it is variable ?

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Sir, Type text is a variable length data type. This is what i know for fact. Now whatever assumption you are making that's going to corrupt it. @manojk @lord_Krishna

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is this valid for attribute or column ?

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I think so.